Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$137.96	11.103%	$153.2777	$153.28	$153.30	$153.30
Purchase #2	$113.92	8.320%	$123.3981	$123.40	$123.40	$123.40
Purchase #3	$151.26	6.383%	$160.9149	$160.91	$160.90	$160.90
Purchase #4	$118.69	8.348%	$128.5982	$128.60	$128.60	$128.60
Purchase #5	$135.48	11.202%	$150.6565	$150.66	$150.65	$150.70
Purchase #6	$239.78	13.308%	$271.6899	$271.69	$271.70	$271.70
Purchase #7	$239.57	10.454%	$264.6146	$264.61	$264.60	$264.60
7 purchase totals =	$1,136.66		$1,253.1499	$1,253.15	$1,253.15	$1,253.20